The digital era that is now upon us has the potential to change the way everyone operates in the motion picture field. The traditional method for projecting motion picture film was relatively simple because there were not very many options available to be controlled. Basically, film has a certain appearance or “look” that can be altered by processing, lighting and laboratory methods. The digital age has brought to the motion picture industry the ability to capture a motion picture print image and structure it in the form of data. Once the data has been captured, it can be manipulated practically to any degree that is desired. However, the more variables one has to work with, the harder it is to maintain or reconstruct the original intent.
In the prior art, digital image processing has taken place on variables associated with video images, as described in U.S. Pat. Nos. 5,335,013, 5,475,425 and 5,831,673, in order to emulate the broadcast look of film or the look of film after it has been through a telecine transfer. These patents describe systems for rendering the output of a video camera to simulate the visual appearance of motion picture film that has been transferred or converted to a video signal to be output directly for television broadcasting or recording on video tape. Further, the above-cited prior art teaches the alteration of the apparent contrast of the video image so the desired broadcast film appearance may be obtained. More specifically, in the '013 patent a gray scale modifier is used as a look-up table (LUT) and the operator can choose between a variety of curves (% light level vs. video level) stored in programmable read-only memory (PROM) to reflect different film types or achieve different photographic effects. The desired curve is selected by pressing a switch on the hardware.
U.S. Pat. Nos. 5,140,414; 5,374,954; 5,406,326; 5,457,491 and 5,687,011 (each issued to Mowry) represent a family of related post-production video technology that seeks to arrive at an aesthetically acceptable simulation of the appearance that images originated on different motion picture film stocks would embody after telecine “flying spot scanner” transfer to video from taped high definition video originated images. One component of this prior art technology deals with the conversion of the video-originated material through a LUT that is based on color temperature of the scene lighting, scene brightness and selected f-stop setting. The conversion values in the LUT are derived by filming color charts and grey scale charts, obtaining a digital representation of the film component responses of the charts from telecine transfer of the film to videotape, and then charting the telecine-derived component responses against video originated images of the same charts under identical lighting conditions. Another component of this prior art technology allows for physically instilling selected film grain patterns to the video images. The final simulated video image is either recorded as a high definition signal, or converted to an NTSC signal and broadcast or displayed.
In the latter two of the aforementioned Mowry patents, the digitized video signal may be sent to a film recorder, which reproduces the component-modified images onto a selected, reversal film stock. The film is chemically processed with a film processor and then optically projected, or scanned to video, digital video, or other electronic media. If the film recording option is employed, these patents specify that it is important that the telecine-derived LUT used in the component modification involves response data which compensates for the inherent color response of the film stock on which the images are being digitally recorded.
Prior art also exists for generating a broadcast film appearance with video or digitally captured images, where the processing occurs inside of the camera. Specifically, setup cards have been described for beta- camcorders and also digital camcorders (see L. J. Thorpe et al, “The HDTV Camcorder and the March to Marketplace Realty”, SMPTE Journal, March 1998, pp. 164–177). These miniature plug-in setup cards facilitate prealignment of the camera to achieve an HD image having attributes similar to those that might otherwise be created from a film origination followed by telecine transfer to HD video. The setup cards can be pre-programmed to store desired digital data settings for aesthetic choices to be made concerning, among other characteristics, color reproduction, tonal reproduction and skin-tone detail.
In a combined approach, U.S. Pat. No. 5,319,465 describes a method using modified camera production and modified post-production processes and equipment to create film-like images. Specifically, the method includes the steps of shooting a benchmark comprising a gray scale chart, a color test chart and two backfocus charts with both a film and a video camera with comparable scene lighting and depth of field. Once the film test benchmark is shot, the film is transferred to videotape utilizing a telecine apparatus, with settings indicative of an industry standard set-up film. The video camera image's hue, saturation, luminance and gamma levels are manipulated to color correct the video camera image to look visually like the transferred film image. After the videotape has been edited, the videotape undergoes color correction in which the videotape benchmark is corrected to match the film test benchmark.
The aforementioned prior art is generally trying to emulate the look of film after it has been telecine-transferred to video. This is desirable to some extent because the telecine system does have some film attributes when broadcasted. However, the prior art neglects the emulation of the look of film origination, as if a negative film has been directly printed and projected through a motion picture system. This is particularly desirable where the digital output is recorded on film for projection. Where the prior art does deal with film recording, as in the latter two of the above-mentioned Mowry patents, it does so in the context of a telecine-transferred benchmark. Moreover, when the prior art alters the tone scale and color of a video or digitally captured image to emulate a film, it is done on the telecine-transferred benchmark. This is an imperfect alteration because it cannot operate upon the scene exposure as seen by a film.
Copending, commonly-assigned U.S. Ser. No. 09/712,500, entitled “System and Method for Processing Electronically Captured Images to Emulate Film Tonescale and Color”, filed Nov. 14, 2000 in the names of K. M. Cirulli, J. C. Brewer and N. M. Rodriguez, provides a system and method for rendering electronically captured images to emulate the appearance in tonescale and color of images captured with motion picture film, and subsequently printed onto another motion picture film and displayed theatrically (negative-positive system). The tonescale and color of an electronically captured image is altered only after it has been shifted to emulate scene exposure as seen by film. Then the shifted electronic exposures are mapped through a predetermined LUT and matrix that imparts a film tonescale and color to the electronically captured image. This method is advantageous because it allows for automation of the image processing with predetermined algorithms. In addition, it does not require color-timing decisions to be made by an operator on a per scene basis, if the video or digital camera set-ups remain constant.
Other prior art also exists for manipulation of digital images to emulate a particular “look”. U.S. Pat. Nos. 5,809,164 and 5,239,370 both describe a color management system for characterizing and re-mapping colors. Both describe the ability to re-map the colors in a linear and non-perceptual process. U.S. Pat. No. 4,839,721 teaches that transformation between a capture medium the selected color is essentially a linear response.
The prior art generally cited above describes the conversion of an electronically captured image from an electronic camera to data that can be written to a film recorder and subsequently printed. Ideally, as represented in the Cirulli et al application Ser. No. 09/712,500, the image chain allows for a match between the print generated by this process and a print from a film captured scene (“print” as used herein refers to the final transparency used for projection).
What is needed is a system that converts a scanned film image into data that can be displayed on an electronic display device, such as a digital projector, and still look like a projected film image. The projected digital image would correctly replicate the look of film origination, particularly as to film tonescale and color reproduction, as if a negative film has been directly printed and projected through a motion picture system.